Method of glazing refractory bodies



Patented Feb. 5, 1935 Robert F. Rennie, Bloomfield, N. J., assignor to Westinghouse Lamp of Pennsylvania No Drawing.

9 Claims.

I ture of electrical devices as for example electric incandescent lamps.

In the manufacture of electric lamps it is desirable to provide the filament supporting structure with portions made of insulative refractory spacers, cross pieces or other parts which will not release occluded gases under the temperature at which the device is operative.

It has been the practice in some cases to use lava for the refractory supporting portions of a lamp structure. It has been found, however, that lava holds gases which, when released, are detrimental to the life of the lamp or other vacuum or gas device in which the parts are used.

In accordance with the present invention a refractory part such as one shaped from lava or from porcelain is provided with a glazed surface. Glazed surfaces have heretofore been produced particularly with porcelain by means of salts applied to the parts while in a kiln. But this method is unsatisfactory for the manufacture of small parts which must be completely covered with a glaze.

I have found that glazed parts for use as structural parts of incandescent lamps or similar devices may be made by forming an unflred porcelain part to the desired shape and imbedding it in a steatite mixed with a quantity of a compound capable of producing a glaze on the surface when subjected to a given temperature.

I have found that a satisfactory glaze is had by mixing dry sodium silicate with the powder and that, when heat-treated, a sintering or fusing occurs which gives the part a glazed surface when it is covered with the powder and heated in hydrogen.

It is an object of the present invention, therefore, to simplify the method of making shaped refractory elements of the above character for electrical devices.

Another object of the invention is to reduce the time and labor as heretofore attended the making of refractory parts with glazed surfaces.

Another object of the invention is to provide a method of making shaped refractory elements wherein the surfaces become glazed when the shaped element is baked.

It is possible, by reason of the present method, to [glaze refractory parts after they have been connected to other structures. For example an Company, a cdrporatlon Application October 25, 1933. Serial No. 695,166

insulative refractory cross bar may be used to connect several metallic supports as when a mount is made to support a filament. This structure or mount may be completed with the refractory part or parts pressed to shape but not glazed. The entire mount or the refractory portion may be imbedded in the glazing powder and fired with the result that a glaze is formed on the refractory body in a uniform and continuous sheet, filling the cracks and crevices in the form of a smooth layer.

In practice I have obtained good results when parts to be glazed are made from a porcelain slip including the following:

The above constituents may be ball-milled with 100 cc. of water and 2 cc. of sodium silicate. The silicate may be such as the chemical preparation Division's Silicate Binder No. 4.

The glazing compound may be of a steatite having added thereto about .25 per cent of dry sodium silicate NazSiOs. Parts shaped from the above slip may be imbedded in the compound and heated to a temperature between 1200 degrees centigrade and 1230 degrees centigrade in an atmosphere of hydrogen.

At temperatures less than 1190 degrees centigrade, very little glaze will be produced and at temperatures above 1235 degrees centigrade, loose powder will stick to the part treated giving a rough and undesirable surface. The best results have been obtained by heating the mass within the range of temperatures first above mentioned in an atmosphere of hydrogen.

Good results have been obtained when using glazing powders consisting of magnesium oxide, (MgO) containing sodium silicate and of talc containing up to 15 percent magnesium and V to 3'percent sodium silicate and with this mixture a glaze is formed of lower melting point.

Various refractory materials have been tried but the best results have been obtained with porcelain and lava. When using lava the firing temperature may be lower than with porcelain.

The present invention provides a method whereby a refractory body may be glazed by heating in a glazing compound and in the case of porcelain or the like the body is covered with the compound. when glazing a refractory body such as lava the body is disposed in a gaseous atmosphere as for example a hydrogen atmosphere containing the vapors of sodium silicate such as are obtained when heating sodium silicate to about 1150 degrees centigrade.

Although a preferred embodiment of the invention is described herein, it is to be understood that the method may be modified as to the proportions, order of steps employed without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. The method of glazing a refractory body which consists in covering the body with a powder containing a compound fusible on the surface of the body and heating said body in hydrogen.

2. The method of glazing a refractory body which comprises imbedding the bodyin steatite containing a compound fusible on the surface of the body to form'a glazed layer and in heating the body to the fusing temperature of the compound.

3. The method of glazing a refractory body which comprises imbedding the body in steatite containing a compound fusible on the surface of the body and in heating said body in an atmosphere of hydrogen.

4. The method of making a glazed refractory body which comprises shaping a body from a powder containing sodium silicate and heating the body while imbedded in a powder containing steatite.

5. The method of making a glazed refractory.

body which comprises shaping a refractory powder into a compact mass and heating'the mass in a hydrogen atmosphere while imbedded in a powder containing sodium silicate.-

6. The method of making a glazed refractory body which comprises shaping a refractory powder into a compact mass and heating the mass in a hydrogen atmosphere while imbedded in a magnesium compound containing sodium silicate.

7. The method of glazing a refractory body which comprises subjecting the body to vapors obtained when heating sodium silicate.

8. The method of glazing a refractory body which comprises subjecting the body to the vapors obtained when heating the body in hydrogen 1 containing the vapors of sodium silicate.

9. The method of glazing a lava body which comprises subjecting the body to the vapors obtained when heating sodium silicate to about 1150 degrees centigrade in a hydrogen atmosphere. ROBERT F. RENNIE. 

